Substrate processing method

ABSTRACT

A substrate processing method capable of achieving uniform etch selectivity in the entire thickness range of a thin film formed on a stepped structure includes: forming a thin film on a substrate by performing a plurality of cycles including forming at least one layer and applying plasma to the at least one layer under a first process condition; and applying plasma to the thin film under a second process condition different from the first process condition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/906,085, filed on Sep. 25, 2019, and U.S. Provisional Application No.63/054,220, filed on Jul. 20, 2020, in the United States Patent andTrademark Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND 1. Field

One or more embodiments relate to a substrate processing method, andmore particularly, to a substrate processing method that may improve theetch selectivity of a thin film formed on a stepped structure.

2. Description of Related Art

As semiconductor pattern structures are miniaturized and madethree-dimensional, there is an increasing need for new thin filmdeposition techniques that may simplify the process. For example, a 3DNAND flash device has a vertically stacked gate structure and anelectrode wiring structure. In order to interconnect these structures, atechnique of selectively removing a film deposited on a steppedstructure to form a pad structure is required.

In order to selectively remove the film deposited on the steppedstructure, the film is deposited on the stepped structure through aplasma process, and then wet-etched to remove a side film of the steppedstructure, leaving upper and lower films of the stepped structure.However, a method of removing the upper and lower films of the steppedstructure and leaving the side film of the stepped structure may also beused.

This method is possible by controlling plasma to be applied andadjusting characteristics of the upper and lower films or the side filmof the stepped structure. For example, the side film may be removedduring etching by using the straightness of radicals to make the upperand lower films in the direction perpendicular to the direction ofradical progression to be harder than the side film. Conversely, byincreasing the intensity of the plasma to strengthen ion bombardment, abonding structure of the upper film and the lower film may be weakenedrather than the side film to remove the upper film and the lower filmduring etching.

This process may be accomplished by varying plasma applicationconditions. For example, below a certain plasma power or plasma density,thin film densification may be dominant on a thin film surfaceperpendicular to the direction of radical progression. Conversely, abovea certain plasma power or plasma density, a thin film bonding structuremay be weakened on the thin film surface perpendicular to the directionof radical progression.

SUMMARY

One or more embodiments include a substrate processing method that mayimprove the etch selectivity of a thin film by achieving uniform etchselectivity in the entire thickness range of the thin film formed on astepped structure.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

According to one or more embodiments, a substrate processing methodincludes: forming a thin film on a substrate by performing a pluralityof cycles including forming at least one layer and applying plasma tothe at least one layer under a first process condition to the layer; andapplying plasma to the thin film under a second process conditiondifferent from the first process condition.

According to an example of the substrate processing method, anatmosphere may be set such that plasma ions have directionality duringthe applying of the plasma under the first process condition and duringthe applying of the plasma under the second process condition.

According to another example of the substrate processing method, abonding structure of a portion of the thin film may be changed duringthe applying of the plasma under the first process condition, and thebonding structure of a portion of the thin film may be further changedduring the applying of the plasma under the second process condition.

According to another example of the substrate processing method, thesubstrate processing method further includes an isotropic etchingoperation, wherein etch selectivity between the portion where thebonding structure of the thin film is changed and the remaining portionof the thin film may be achieved during the isotropic etching operation.

According to another example of the substrate processing method, the atleast one layer may be formed on a stepped structure having an uppersurface, a lower surface, and a side surface between the upper surfaceand the lower surface, and the portion of the thin film may correspondto a portion of the thin film formed on the upper surface and the lowersurface.

According to another example of the substrate processing method,repetition of the above cycles causes a difference between a firstbonding structure of a first portion of the thin film adjacent to thestepped structure and a second bonding structure of a second portion ofthe thin film away from the stepped structure, and during the applyingof the plasma under the second process condition, the difference betweenthe first bonding structure of the first portion and the second bondingstructure of the second portion may be reduced.

According to another example of the substrate processing method, thesubstrate processing method may further include an isotropic etchingoperation. After the isotropic etching operation, thin films on theupper surface and the lower surface of the stepped structure may beremoved, and a thin film on the side surface of the stepped structuremay remain.

According to another example of the substrate processing method, ahydrogen-containing gas may be supplied during the applying of theplasma under the second process condition.

According to another example of the substrate processing method, theforming of the at least one layer may include: supplying a first gas;purging the first gas; and supplying a second gas and applying plasma toform a first layer.

According to another example of the substrate processing method,pressure in a reaction space is maintained at a first pressure duringthe supplying of the second gas and applying the plasma to form thefirst layer, and the pressure in the reaction space may be maintained ata second pressure lower than the first pressure during the applying ofthe plasma under the first process condition.

According to another example of the substrate processing method, powersupplied during the applying of the plasma under the first processingcondition is greater than power supplied during the supplying of thesecond gas and the applying of the plasma to form the first layer.

According to another example of the substrate processing method, thefirst gas may be supplied during the applying of the plasma under thesecond process condition that is different from the first processcondition.

According to another example of the substrate processing method, duringa first cycle, the supplying of the first gas, the purging of the firstgas, and the supplying of the second gas and applying of plasma to formthe second layer may be performed a plurality of times.

According to another example of the substrate processing method, duringthe first cycle, the plasma under the first process condition is appliedto the first layer so that a WER of a portion of the first layer mayincrease due to an ion bombardment effect of the plasma ions.

According to another example of the substrate processing method, formingof a second layer on the first layer during a second cycle after thefirst cycle is performed, wherein the forming of the second layer mayinclude: supplying the first gas; purging the first gas; and supplyingthe second gas and applying the plasma to form the second layer.

According to another example of the substrate processing method, duringthe second cycle, the plasma under the first process condition isapplied to the second layer and the first layer which is below thesecond layer so that WERs of a portion of the first layer and a portionof the second layer may increase due to an ion bombardment effect of theplasma ions, wherein the WER of the first layer may be greater than theWER of the second layer.

According to another example of the substrate processing method, theplasma under the second process condition is applied toward the firstlayer and the second layer, and thus the difference between the WER ofthe first layer and the WER of the second layer may be reduced.

According to one or more embodiments, a substrate processing methodincludes: forming a first layer; applying first plasma to the firstlayer to change characteristics of a portion of the first layer; forminga second layer on the first layer; applying second plasma to the firstlayer and the second layer to change characteristics of respectiveportions of the first layer and the second layer; and applying thirdplasma to the second layer to reduce a difference between thecharacteristics of the portion of the first layer and thecharacteristics of the portion of the second layer.

According to an example of the substrate processing method, a firstprocess condition may be used during the application of the first plasmaand the application of the second plasma, and a second process conditionthat is different from the first process condition may be used duringthe application of the third plasma.

According to one or more embodiments, a substrate processing methodincludes: forming a thin film on a substrate by performing a cycleincluding supplying a first gas onto a substrate and supplying a secondgas having reactivity with the first gas a plurality of times, wherein,due to repetition of the cycle, a first portion of the thin filmadjacent to the substrate has a higher WER than that of a second portionof the thin film away from the substrate; and reducing a differencebetween the WER of the first portion and the WER of the second portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a flowchart of a substrate processing method according toembodiments;

FIG. 2 is a view of a substrate processing method according toembodiments;

FIG. 3 is a view of a substrate processing method according toembodiments;

FIG. 4 is a view of a substrate processing device in which a substrateprocessing method is performed;

FIG. 5 is a view of a thin film formed on a stepped structure and a filmremaining after isotropic etching;

FIG. 6 is a view of a substrate processing method according toembodiments;

FIG. 7 is a graph showing a change in a wet etch rate in a thin film;

FIG. 8 is a view of a state in which a thin film formed on a steppedstructure remains after isotropic etching;

FIG. 9 is a view of a substrate processing method according toembodiments;

FIG. 10 is a graph showing etching characteristics of a thin film aftera process according to the disclosure;

FIG. 11 is a view of the etch selectivity of a thin film obtainedaccording to different substrate processing methods;

FIG. 12 is a view of a substrate processing method according toembodiments;

FIG. 13 is a view of a substrate processing method according toembodiments;

FIG. 14 is a view of a substrate processing method according toembodiments;

FIG. 15 is a view of a state in which a thin film formed by theabove-described substrate processing methods remains after isotropicetching;

FIG. 16 illustrates a substrate processing method according toembodiments of the disclosure; and

FIGS. 17A and 17B illustrate a degree of wet etching of a thin film on asidewall of a pattern structure according to the presence or absence ofplasma purging in accordance with examples of the disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentembodiments may have different forms and should not be construed asbeing limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects of the present description. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various members, components, regions, layers,and/or sections, these members, components, regions, layers, and/orsections should not be limited by these terms. These terms do not denoteany order, quantity, or importance, but rather are only used todistinguish one component, region, layer, and/or section from anothercomponent, region, layer, and/or section. Thus, a first member,component, region, layer, or section discussed below could be termed asecond member, component, region, layer, or section without departingfrom the teachings of embodiments.

In the disclosure, “gas” may include evaporated solids and/or liquidsand may include a single gas or a mixture of gases. In the disclosure, aprocess gas introduced into a reaction chamber through a shower head mayinclude a precursor gas and an additive gas. The precursor gas and theadditive gas may typically be introduced as a mixed gas or may beseparately introduced into a reaction space. The precursor gas may beintroduced together with a carrier gas such as an inert gas. Theadditive gas may include a dilution gas such as a reaction gas and aninert gas. The reaction gas and the dilution gas may be mixedly orseparately introduced into the reaction space. The precursor may includetwo or more precursors, and the reaction gas may include two or morereaction gases. The precursor may be a gas that is chemisorbed onto asubstrate and typically contains metalloid or metal elementsconstituting a main structure of a matrix of a dielectric film, and thereaction gas for deposition may be a gas that is reactive with theprecursor chemisorbed onto the substrate when excited to fix an atomiclayer or a monolayer on the substrate. The term “chemisorption” mayrefer to chemical saturation adsorption. A gas other than the processgas, that is, a gas introduced without passing through the shower head,may be used to seal the reaction space, and it may include a seal gassuch as an inert gas. In some embodiments, the term “film” may refer toa layer that extends continuously in a direction perpendicular to athickness direction without substantially having pinholes to cover anentire target or a relevant surface, or may refer to a layer that simplycovers a target or a relevant surface. In some embodiments, the term“layer” may refer to a structure, or a synonym of a film, or a non-filmstructure having any thickness formed on a surface. The film or layermay include a discrete single film or layer or multiple films or layershaving some characteristics, and the boundary between adjacent films orlayers may be clear or unclear and may be set based on physical,chemical, and/or some other characteristics, formation processes orsequences, and/or functions or purposes of the adjacent films or layers.

In the disclosure, the expression “containing an Si—N bond” may bereferred to as characterized by an Si—N bond or Si—N bonds having a mainskeleton substantially constituted by the Si—N bond or Si—N bonds and/orhaving a substituent substantially constituted by the Si—N bond or Si—Nbonds. A silicon nitride layer may be a dielectric layer containing aSi—N bond, and may include a silicon nitride layer (SiN) and a siliconoxynitride layer (SiON).

In the disclosure, the expression “same material” should be interpretedas meaning that main components (constituents) are the same. Forexample, when a first layer and a second layer are both silicon nitridelayers and are formed of the same material, the first layer may beselected from the group consisting of Si2N, SiN, Si3N4, and Si2N3 andthe second layer may also be selected from the above group but aparticular film quality thereof may be different from that of the firstlayer.

Additionally, in the disclosure, according as an operable range may bedetermined based on a regular job, any two variables may constitute anoperable range of the variable and any indicated range may include orexclude end points. Additionally, the values of any indicated variablesmay refer to exact values or approximate values (regardless of whetherthey are indicated as “about”), may include equivalents, and may referto an average value, a median value, a representative value, a majorityvalue, or the like.

In the disclosure where conditions and/or structures are not specified,those of ordinary skill in the art may easily provide these conditionsand/or structures as a matter of customary experiment in the light ofthe disclosure. In all described embodiments, any component used in anembodiment may be replaced with any equivalent component thereof,including those explicitly, necessarily, or essentially describedherein, for intended purposes, and in addition, the disclosure may besimilarly applied to devices and methods.

Hereinafter, embodiments of the disclosure will be described withreference to the accompanying drawings. In the drawings, variations fromthe illustrated shapes may be expected as a result of, for example,manufacturing techniques and/or tolerances. Thus, the embodiments of thedisclosure should not be construed as being limited to the particularshapes of regions illustrated herein but may include deviations inshapes that result, for example, from manufacturing processes.

FIG. 1 is a flowchart of a substrate processing method according toembodiments of the present invention.

Referring to FIG. 1, the substrate processing method may includeoperation S110 of forming at least one layer and operation S120 ofapplying plasma under a first process condition. Operations S110 andS120 may be repeated a plurality of times as one group-cycle, and a thinfilm may be formed on a substrate by the repetition. The substrateprocessing method may further include operation S150 of applying plasmaunder a second process condition different from the first processcondition.

During operation S110 of forming at least one layer, a thin film may beformed on a stepped structure. That is, the thin film may be formed onthe stepped structure having an upper surface, a lower surface, and aside surface between the upper surface and the lower surface. Thestepped structure may be a structure having a high aspect ratio, and theaspect ratio may be, for example, greater than or equal towidth:height=1:10. To form a conformal thin film on the steppedstructure with such a high aspect ratio, an atomic layer deposition(ALD) process may be used. In particular, a plasma atomic layerdeposition process (PEALD) may be used.

During operation S110 of forming at least one layer, the atmosphere maybe set such that an average free path of plasma ions is reduced and theplasma ions are not directional (i.e., such that random movement of theplasma ions is increased). Such an atmosphere may contribute to forminga conformal thin film on a stepped structure with a high aspect ratio.In order to achieve the above atmosphere, a high pressure atmosphere(e.g., 10 to 20 Torr) may be formed. In another embodiment, in order toachieve the above atmosphere, a low power atmosphere (e.g., 200 W to 500W) may be formed. In another embodiment, in order to achieve the aboveatmosphere, a high temperature atmosphere may be formed.

During operation S110 of forming of at least one layer, a layer may beformed using plasma. For example, operation S110 may include supplying afirst gas, purging the first gas, and supplying a second gas andapplying plasma to form a first layer. By applying the plasma, a secondgas may be excited to become reactive, and the reactive second gas mayreact with the first gas to form the first layer.

The first gas may include a material that is chemisorbed on thesubstrate as a source gas. The second gas may include a materialreactive with the first gas, in particular a material reactive with thefirst gas under a plasma atmosphere. In an alternative embodiment, thesupplying of the second gas and the applying of the plasma may beperformed simultaneously. In another embodiment, after the supplying ofthe second gas, the applying of the plasma may be performed.

Operation S110 of forming at least one layer may be performed aplurality of times (e.g., a cycles). In more detail, a group-cycle GCincluding operation S110 of forming at least one layer and operationS120 of applying the plasma under the first process condition may beperformed a plurality of times. Operation S110 of forming at least onelayer may be performed a plurality of times during one group-cycle GC.Therefore, during one cycle, the supplying of the first gas, the purgingof the first gas, and the supplying of the second gas and the applyingof plasma to form the second layer, which are included in operation S110of forming at least one layer, may be performed a plurality of times.

After operation S110 of forming at least one layer, operation S120 ofapplying the plasma under the first process condition is performed.Operation S120 of applying the plasma under the first process conditionmay be performed for a certain time (e.g., b seconds). By applying theplasma under the first process condition, a bonding structure of aportion of the at least one layer may be changed. During operation S120of applying the plasma under the first process condition, the plasmaions may be set to be directional. On the other hand, as describedabove, during operation S110 of forming the at least one layer, theplasma ions may be set to have no directionality.

The directional plasma ions may change a bonding structure of a portionof the thin film. For example, in a case where a thin film is formed ona stepped structure having an aspect ratio, the directivity of plasmaions may be set to face an upper surface or a lower surface of thestepped structure. In this case, the plasma ions may change a bondingstructure of a thin film formed on the upper or lower surface of thestepped structure. In contrast, the directional plasma ions may notaffect a bonding structure of a thin film formed on the side of thestepped structure.

As described above, in operation S110 of forming at least one layer, thepressure in a reaction space may be maintained at a first pressure(e.g., a high pressure) while supplying the second gas and applying theplasma so that random movement of the reaction gas may be increased. Incontrast, in operation S120 of applying the plasma under the firstprocess condition, the pressure in the reaction space may be maintainedat a second pressure (e.g., a lower pressure) less than the firstpressure so that the movement of the reaction gas is directional.

Furthermore, in operation S110 of forming at least one layer, powersupplied during operation S110 may be maintained at a first power value(e.g., a low power value) so that the reaction gas is less affected bythe power (i.e., the plasma ions become not directional). In contrast,in operation S120 of applying the plasma under the first processcondition, power supplied during operation S120 may be maintained at asecond power value (e.g., a high power value) that is higher than thefirst power value so that the reaction gas is more affected by the power(i.e., the plasma ions become directional).

Operation S110 of forming at least one layer and operation S120 ofapplying the plasma under the first process condition may be defined asone group-cycle GC, and the group-cycle GC may be repeatedly performed.In other words, in operation S100, the X value is set to 1 beforeperforming the group-cycle GC, and in operation S140, after performingthe group-cycle GC including operation S110 of forming at least onelayer and operation S120 of applying the plasma under the first processcondition, the X value is increased, and when the X value reaches acertain value in operation S130, the group-cycle GC is terminated andsubsequent operations may be performed.

As a subsequent operation, operation S150 of applying plasma under thesecond process condition is performed. Operation S150 of applying theplasma under the second process condition may be performed for a certaintime (e.g., y seconds). By applying the plasma under the second processcondition, a bonding structure of a portion of the at least one layermay be further changed. During operation S150 of applying the plasmaunder the second process condition, the plasma ions may be set to bedirectional.

For example, the plasma ions may be set to be directed towards at leastone layer. In this case, since plasma ions are incident at least towardsthe layer, a portion where the bonding structure of the at least onelayer is changed will be a portion formed on upper and lower surfaces ofa pattern structure. When power of the plasma is above a thresholdvalue, portions formed on an upper surface and a lower surface of the atleast one layer will be weakened, and when power of the plasma is belowa threshold value, portions formed on an upper surface and a lowersurface of the at least one layer will be dense.

Both operation S120 of applying the plasma under the first processcondition and operation S150 of applying the plasma under the secondprocess condition are common in that they change the bonding structureof the thin film. However, since the first process condition and thesecond process condition are different, a thickness range of a thin filmwhich bonding structure is changed by the first process condition isdifferent from a thickness range of a thin film which bonding structureis changed by the second process condition.

In more detail, when a cycle including operation S110 of forming atleast one layer and operation S120 of applying the plasma under thefirst process condition is repeated, in the case of initially formedlayers (i.e., a first portion of a thin film adjacent to the steppedstructure), changes in the bonding structure due to the plasmaapplication may be accumulated. Meanwhile, in the case of later formedlayers (i.e., a second portion of a thin film away from the steppedstructure), only a few plasma applications (or one plasma application)are performed, so the change in the bonding structure may be relativelyless.

To offset this partial difference in the bonding structure, the plasmaunder the second process condition may be applied. For example, theplasma under the second process condition may be applied to cause achange in the bonding structure of the second portion of the thin filmaway from the stepped structure and to not affect the bonding structureof the first portion of the thin film adjacent to the stepped structure.By applying the plasma under the second process condition, a differencebetween the bonding structure of the first portion and the bondingstructure of the second portion may be reduced.

In an embodiment, a hydrogen-containing gas may be supplied duringoperation S150 of applying the plasma under the second processcondition. By performing plasma treatment using the hydrogen-containinggas, more Si—H bonds may be formed in the second portion of the thinfilm away from the stepped structure. Therefore, the etch rate of acorresponding portion may be increased in the subsequent etchingprocess.

In another embodiment, the same gas as the gas supplied in operationS150 of forming at least one layer may be supplied during operation S150of applying the plasma under the second process condition. For example,supplying a first gas (e.g., the source gas), purging the first gas, andsupplying a second gas (e.g., the reaction gas) and applying the plasmato form the first layer may be performed during operation S110 offorming at least one layer. The first gas (e.g., the source gas) may besupplied during operation S150 of applying the plasma under the secondprocess condition.

In this case, a thin film may be additionally formed on a side surfaceof a stepped structure while maintaining an ion bombardment effect onthe surfaces of thin films formed on an upper surface and a lowersurface of the stepped structure by the applying of the plasma under thesecond process condition. This is particularly advantageous in the caseof weakening a bonding structure of a thin film because a thin film isfurther formed on the side surface of the stepped structure while thethin films formed on the upper surface and the lower surface areweakened by the directional plasma, thereby increasing the etchselectivity. Furthermore, due to the source gas supplied during theplasma application, an ion bombardment effect of the plasma ions on thethin film formed on the side surface may be reduced.

After operation S150 of applying the plasma under the second processcondition, operation S160 of isotropic etching on a thin film formed byperforming a plurality of group-cycles is performed. For example, wetetching of the thin films may be performed. For example, wet etching maybe performed by immersing a substrate on which a semiconductor device,such as a thin film, is deposited, in a liquid etching solution andetching the surface by a chemical reaction. Since such wet etching isisotropic etching, such isotropic etching itself may not significantlyaffect elective etching of the thin film formed on the steppedstructure.

During operation S160 of isotropic etching, the etch selectivity betweena portion where a bonding structure of the thin film is changed and theremaining portion of the thin film may be achieved. In other words, byperforming operation S120 of applying the plasma under the first processcondition and operation S150 of applying the plasma under the secondprocess condition, the bonding structure of a portion of the thin film(the thin films on the upper and lower surfaces of the steppedstructure) on the stepped structure is changed, so that a portion of thethin film may be removed and other portions may remain during theisotropic etching. By removing a portion of the thin film on the steppedstructure, a surface of the stepped structure may be exposed. Therefore,selective etching of the thin film may be achieved by a subsequentetching process. Thus, a patterned thin film formed on an area of astepped structure may be formed without a separate additionalphotolithography process.

According to embodiments of the inventive concept, a combination ofoperation S120 of applying the plasma under the first process conditionand operation S150 of applying the plasma under the second processcondition different from the first process condition are used. Bycombining and applying plasmas having such different process conditions,it is possible to achieve uniform etch selectivity over the entirethickness range of the thin film formed on the stepped structure,compared to a case where only plasma of a one-type process condition isapplied.

When only operation S120 of applying the plasma under the first processcondition is performed, as the cycle is repeated, an area where plasmais applied several times occurs. Therefore, the etch selectivityincreases in a deep portion of the thin film by applying the plasmaseveral times, whereas the etch selectivity decreases relatively in asurface of the thin film. With low etch selectivity at the surface,productivity is reduced because a thickness of the thin film needs to bedeposited thicker than a target thickness in order to form a side filmof an appropriate thickness.

When only operation S150 of applying the plasma under the second processcondition is performed, a high etch selectivity may be achieved by anion bombardment effect and/or penetration of active species (e.g.,hydrogen ions) into the thin film. However, the possibility of defectsin the substrate is increased by the bombardment effect and thepenetration of active species. In order to prevent this, when a plasmapower is reduced or a penetration force of the active species islowered, the problem that etch selectivity at the deep portion (i.e.,the portion adjacent to the stacked structure and/or the substrate) ofthe thin film is lowered occurs. As a result, the thickness of the thinfilm needs to be deposited thicker than the target thickness in order toform a side film of an appropriate thickness, thereby reducingproductivity.

By performing the combination of operation S120 of applying the plasmaunder the first process condition and operation S150 of applying theplasma under the second process condition different from the firstprocess condition, the disadvantages of each of them may becomplemented. In other words, by the combination, a markedly improvedeffect may be achieved compared to the case of performing only anindividual plasma application process.

A change in the bonding structure of a portion of the thin film byplasma ions may be weakening of the bonding structure, or may bedensification of the bonding structure. Hereinafter, embodiments will bedescribed in more detail on the premise of the weakening the bondingstructure.

An atmosphere may be set such that plasma ions have directionalityduring operation S120 of applying plasma under the first processcondition and operation S150 of applying the plasma under the secondprocess condition. The binding structure of a portion of the thin filmmay be weakened by the ion bombardment effect of the directional plasmaions.

In more detail, the plasma ions may have a direction perpendicular tothe upper and lower surfaces of the stepped structure. Therefore, thebonding structure of the upper and lower surfaces of the thin film maybe weakened. As a result, by the subsequent operation S160 of isotropicetching, the thin films on the upper surface and the lower surface ofthe stepped structure may be removed, and a thin film on the sidesurface of the stepped structure may remain.

During a first group-cycle, operation S110 of forming at least one layermay be performed to have a plurality of sub cycles. During theindividual sub cycles, supplying a first gas, purging the first gas, andsupplying a second gas and applying plasma to form a first layer may beperformed.

During the first group-cycle and after the sub cycles, the plasma underthe first process condition may be applied for a certain time. Byapplying the plasma under the first process condition to the firstlayer, a wet etch rate (WER) of a portion of the first layer mayincrease due to the ion bombardment effect of the plasma ions.

This ends the first group-cycle and starts the second group-cycle.During the second group-cycle, operation S110 of forming at least onelayer may be performed to have a plurality of sub cycles. A second layerformed during the second group-cycle will be formed on the first layer.During the individual sub cycle of the second group-cycle, supplying afirst gas, purging the first gas, and supplying a second gas andapplying plasma to form the second layer may be performed.

During the second group-cycle and after the sub cycle for forming thesecond layer, the plasma under the first process condition may beapplied for a certain time. By applying the plasma under the firstprocess condition to the second layer, a WER of a portion of the secondlayer may increase due to the ion bombardment effect of the plasma ions.Meanwhile, the applied plasma may affect not only the second layer butalso the first layer below the second layer. Thus, the WER of a portionof the first layer may further increase, and consequently the WER of thefirst layer may be greater than the WER of the second layer.

After the first group-cycle and the second group-cycle, the plasma underthe second process condition may be applied toward the first layer andthe second layer. As described above, the second process condition maybe different from the first process condition. In particular, the secondprocess condition may be a process condition that weakens the secondlayer of the upper portion but does not significantly affect the firstlayer of the lower portion. For example, the second process conditionsmay produce an active species having low penetration, and the activespecies may only weaken the upper second layer and not significantlyaffect the weakening of the lower first layer. As a result, by applyingthe plasma of the second process, the difference between the WER of thefirst layer and the WER of the second layer may be reduced.

Although it is described in this disclosure that the plasma under thesecond process condition is applied after the second group-cycle, anadditional group-cycle may be performed between the second group-cycleand the plasma application under the second process condition. Forexample, a third group-cycle may be performed after the secondgroup-cycle. During the third group-cycle, operation S110 of forming atleast one layer may be performed to have a plurality of sub cycles. Athird layer formed during the third group-cycle will be formed on thefirst layer and the second layer.

Subsequently, the plasma under the first process condition is applied tothe third layer, and due to the ion bombardment effect of the plasmaions, WERs of portions (portions on an upper surface and a lower surfaceof the stepped structure) may increase (see FIG. 6). As the cyclerepeats, the first portion (e.g., the first layer) of the thin filmadjacent to the substrate will have a higher WER than that of the secondportion (e.g., the second layer) of the thin film away from thesubstrate.

The plasma application under the second process condition performedafter the group-cycle is performed for the purpose of reducing thedifference in the WERs. In other words, by repeating the group-cycle,the plasma under the first process condition is repeatedly applied toincrease the etch selectivity of the deep portion of the thin film,whereas the etch selectivity of the surface of the thin film is lowered.Therefore, the plasma under the second process condition is applied tosolve this problem. By applying the plasma under the second processcondition, the etch selectivity of the surface of the thin film may beincreased, and thus uniform etch selectivity may be achieved regardlessof the thickness (or depth) of the thin film.

FIG. 2 is a view of a substrate processing method according toembodiments. The substrate processing method according to theembodiments may be a variation of the substrate processing methodaccording to the above-described embodiments. Hereinafter, repeateddescriptions of the embodiments will not be given herein.

According to embodiments of the inventive concept, a substrateprocessing method may be proposed to increase the WERs of filmsdeposited on the upper portion and the lower portion of the steppedstructure and to make the WERs constant over time. For example, a firstsub-step of evenly depositing a hard and uniform thin film on thestepped structure, and a second sub-step of performing plasma treatmentto increase the etch selectivity of thin films deposited on a sideportion, upper portion, and lower portion of the stepped structure, anda third sub-step of performing plasma treatment using ahydrogen-containing gas (e.g., H2) may be performed.

Referring to FIG. 2, during the first sub-step (Step 1), a hard anduniform SiN film is evenly deposited on the stepped structure. Forexample, the SiN film may be deposited by plasma atomic layerdeposition. The first sub-step (Step 1) may be repeated a times and anSiN film having a certain thickness may be formed. During the secondsub-step (Step 2), plasma treatment is performed for b seconds (sec).The first sub-step and the second sub-step are made into onegroup-cycle, and the film is repeatedly deposited a plurality of times(x cycles) according to a required thickness. In the first sub-step(Step 1), a high process pressure and a low plasma power are applied toweaken the directivity (straightness) of a plasma active species andevenly deposit a hard and uniform SiN film in the stepped structure. Inthe second sub-step (Step 2), the etch selectivity of the thin filmsdeposited on the side portion, upper portion, and lower portion of thestepped structure is increased by supplying a low process pressure and ahigh plasma power to enhance the directivity (straightness) of theplasma active species.

The third sub-step (Step 3) is a plasma treatment step using ahydrogen-containing gas, which is maintained for y seconds (sec). Thelow pressure and the high plasma power are maintained so that H ionsproduced by the hydrogen-containing gas easily penetrate into the film.The H ions may form weak bonding with SiN or weaken an Si—N bondingstructure. The weakening of the bonding structure by the H ions maymaximize the effect at a surface where the plasma treatment is directlyperformed. Here, a low H2 flow rate is maintained to prevent pile-up ofthe H ions (i.e., to prevent weakening of the thin film in the deepportion). For example, in the third sub-step (Step 3), the H2 flow ratemay be performed under a condition of 100 sccm or less. The thirdsub-step (Step 3) is a step of adjusting the etch selectivity at asurface of the deposited film to be similar to the etch selectivity atthe deep portion of the deposited film.

In an alternative embodiment, in the plasma treatment of the thirdsub-step (Step 3), in addition to the hydrogen-containing gas, othergases that can be easily penetrated into the film may be used. Gasessuch as He to Ar may be used. Wet etching is then performed to retain anSiN film on a sidewall and remove the SiN films on an upper wall and alower wall.

FIG. 3 is a view of a substrate processing method according toembodiments. FIG. 4 is a view of a substrate processing device in whicha substrate processing method is performed. The substrate processingmethod according to the embodiments may be a variation of the substrateprocessing method according to the above-described embodiments.Hereinafter, repeated descriptions of the embodiments will not be givenherein.

Referring to FIG. 4, the substrate processing device may include atleast one reactor. An upper electrode connected to an RF generator, forexample, a showerhead and a lower electrode disposed opposite to theupper electrode may be disposed in the reactor. A substrate may beloaded on the lower electrode, such as a heater block, and a plasmaprocess may be performed on the substrate. In some embodiments, thereactor may be a direct plasma reactor.

A layer formed on the substrate using the substrate processing devicemay be a silicon nitride layer. A plasma atomic layer deposition (PEALD)process may be used to form the silicon nitride layer. As an Si source,a precursor of dichlorosilane (SiH2Cl2), aminosilane, or iodosilane maybe used. As a nitrogen source, a nitrogen gas may be used. The nitrogengas reacts with a physisorbed silicon source on the substrate whenactivated by plasma, but does not react with the silicon source when notactivated by the plasma and may be used as a purge gas.

Referring to FIG. 3, a group-cycle includes two sub-steps of the firstsub-step (Step 1) and the second sub-step (Step 2), and each sub-stepmay be repeated in a cycles and b cycles, respectively. These sub-stepsmay be included in a group cycle, which may be repeated. The firstsub-step (step1) is a step of uniformly depositing an SiN film on apattern structure, and the second sub-step (step2) is a plasma treatmentstep.

During the second sub-step (step2), a bonding structure of an SiN filmdeposited on an upper surface of the pattern structure in a directionperpendicular to the traveling direction of a radical may be weakened.Therefore, in the second sub-step (Step2), in order to enhance a plasmaion bombardment effect, an atmosphere having a lower process pressureand a higher plasma power may be set as compared with the first sub-step(Step1). After the group-cycle, wet etching on the substrate isperformed in a 100:1 diluted hydro fluoride (DHF) solution, and as aresult, the SiN film deposited on the upper surface of the patternstructure is removed and an SiN film deposited on a side surface of thepattern remains.

Meanwhile, during the wet etching, not only an SiN film deposited on anupper surface of the stepped structure but also an SiN film deposited ona side surface of the stepped structure are simultaneously etched.However, an etch rate of the SiN film on the upper surface is high, andas a result, the SiN film on the side surface remains. That is, in orderto realize an SiN film on a sidewall of a desired thickness, a thickerSiN film needs to be formed when the SiN film is actually deposited. Inother words, when the etch rate of the SiN film on the upper surface ofthe pattern structure is faster, the SiN film on the sidewall may berealized with the same thickness even if a less thick SiN film is formedduring deposition. This will save process time and speed up substrateprocessing per hour. FIG. 5 shows such a process, wherein FIG. 5 (a)shows an SiN film formed on a stepped structure, and FIG. 5 (b) shows anSiN film on a sidewall of the stepped structure remaining after wetetching.

Referring to FIG. 5 (a), the SiN film is deposited to a uniformthickness on the pattern structure (upper film d=side film c in the FIG.5A). Since a bonding structure of the upper SiN film is broken by thesecond sub-step (Step 2) of FIG. 3, the upper SiN film d is etchedfaster than the side SiN film c during wet etching. The thickness on theside SiN film is also removed to some extent, but the etch rate of theside SiN film is slower than that of the upper SiN film. Therefore, onlythe side SiN film (a in FIG. 5 (b)) remains after the wet etching (seeFIG. 5 (b)). That is, in order to implement a side film of a desiredthickness, an additional film b needs to be formed considering an etchrate of the upper film d.

In other words, an etch rate Ed of the upper film d and an etch rate Ecof the side film c determine the selectivity, and the faster the etchrate Ed on the upper surface, the better the selectivity will be. Asshown in FIG. 5, a film (a+b) thicker than the side film a of thedesired thickness is deposited considering the difference in the etchrates of the upper film d and the side film c.

FIG. 6 shows a substrate processing method according to the embodimentof FIG. 3. Referring to FIG. 6, a first SiN layer a, a second SiN layerb, and a third SiN layer c are sequentially formed according to anatomic layer deposition method. A nitrogen plasma treatment (Step 2) isperformed for each layer during one cycle. For the sake ofunderstanding, in this embodiment, three group-cycles GC1, GC2, and GC3are shown to be performed (x=3), and the nitrogen plasma treatment(Step2) is performed only once for each layer (b=1).

In FIG. 6, the nitrogen plasma treatment performed for each group-cycleis indicated by an asterisk. The first indication GC1 shows a nitrogenradical applied during a group-cycle of depositing a first layer a, thesecond indication GC2 shows nitrogen radicals applied during agroup-cycle of depositing a second layer b, and the third marking GC3shows nitrogen radicals applied during a group-cycle of depositing athird layer c.

For example, since the nitrogen plasma treatment is performed byapplying a plasma power higher than a critical plasma power, nitrogenradicals destroy the bonding structure of the SiN layer deposited on theupper surface of a pattern. Although nitrogen plasma is applied in theabove experiments, the bonding structure of the film may be more easilybroken by applying Ar plasma with big and heavy elements.

As shown in FIG. 6, it should be noted that plasma applied in the secondsub-step (Step2), which is a plasma treatment step, when each film aredeposited, also affects a lower film. That is, when forming each layer,the nitrogen plasma treatment proceeds only one cycle (b=1) in thesecond sub-step (Step2) in the group-cycle, but a lower layer is furthersubjected to plasma treatment. In other words, when sequentiallydepositing the first layer a, the second layer b, and the third layer c,the first layer a adjacent to a pattern structure is subjected to threeplasma treatments, the second layer b on the first layer a is subjectedto two plasma treatments, and the third layer c away from the patternstructure is subjected to one plasma treatment. This means that theetching characteristics in the whole bulk film (a+b+c) are not uniformand the WER is higher toward the lower portion of the film (Ea<Eb<Ec).

FIG. 7 shows a change in the wet etch rate in the SiN thin film which isthe bulk film according to FIG. 6. A horizontal axis represents a changein an etching time, and a vertical axis represents a change in an etchrate according to the etching time. The relationship between thehorizontal axis and the vertical axis corresponds to a change in theetch rate inside the film from the surface of the bulk film to theinside. As shown in the graph, it can be seen that the etch rate is notuniform from the surface of the SiN thin film to a deep portion. Thatis, it can be seen that the WER is less at a surface portion of the SiNthin film that is applied with less plasma, and the WER is great at thedeep portion of the SiN thin film that is applied with a large amount ofplasma by repeating the group-cycle.

When wet etching characteristics of the bulk film are not uniform, theselectivity between an upper surface and a side surface is reduced. Forexample, when the etch rate of a thin film on the upper surface is lessin an initial stage of a wet etching process subsequent to a depositionprocess, as much of a thin film on the side surface is etched as thefilm on the upper surface is etched. On the contrary, when the etch rateof the deep portion of the thin film is less in a late wet etchingprocess subsequent to the deposition process, the thin film on the sidesurface is etched as much while etching the deep portion of the film. Asa result, as shown in FIG. 8, when a thin film on an upper portion of apattern structure is etched, only a thin film having a thickness e lessthan or equal to the desired thickness a remains on the side surface,and as a result, the selectivity between an upper thin film and a sidethin film is reduced.

Therefore, in consideration of this problem, the thin film needs to bedeposited to have a relatively thick thickness in a thin film formingoperation. This means that the increased source and gas consumptionincreases the cost of ownership (COO) of a device and lowers substratethroughput per unit time.

FIG. 9 is a view of a substrate processing method according toembodiments. The substrate processing method according to theembodiments may be a variation of the substrate processing methodaccording to the above-described embodiments. Hereinafter, repeateddescriptions of the embodiments will not be given herein.

Referring to FIG. 9, disclosed is a substrate processing method capableof improving the selectivity in a bulk film by making an etch rate ofthe bulk film uniform throughout its entire thickness. This substrateprocessing method may be performed in a direct plasma deposition devicecomposed of upper and lower electrodes, shown in FIG. 4.

In the embodiment shown in FIG. 9, the third sub-step (Step 3) forperforming post plasma treatment is added as compared to the embodimentof FIG. 3. First, two sub-steps (Step1 and Step2) are repeated severaltimes. That is, the first sub-step (Step 1) is repeated a cycles, andthe second sub-step (Step 2) is repeated b cycles. Then, a group-cycleis performed so that this repetition is repeated several times (x cyclerepetition). After a group step is completed, the third sub-step (Step3) for the post plasma treatment is performed. The post plasma treatmentmay be repeated several times (e.g., y cycles). Each step will bedescribed in more detail later below.

1. First Sub-Step (Step 1): Conformal Deposition

This step is a step of depositing an SiN film on a pattern as the firstsub step. Since the SiN film of a uniform thickness is deposited,thicknesses of SiN films deposited on an upper portion and a sideportion of the pattern are the same. A source gas of halide series (e.g.dichlorosilane (DCS)) or aminosilane or iodosilane series may be used asa silicon source, and a nitrogen gas may be used as a nitrogen source.The nitrogen gas, when activated with plasma, reacts with the siliconsource to be the component of a film, but may be used as a purge gaswithout reacting with the silicon source when not activated with plasma.

During the first sub-step, the SiN film is uniformly applied on apattern structure while the source gas, a reactor gas, and the plasmaare alternately supplied and repeated several times (a cycles) by aPEALD method. A plasma power is weakened to allow radicals to besupplied to the inside of the pattern. The plasma power is supplied from200 watts to 900 watts, preferably 500 watts.

In addition, by increasing process pressure to weaken straightness ofthe radicals to allow more radicals to be supplied to a pattern sidesurface than a pattern bottom surface, thereby facilitating formation ofthe SiN film on the side portion. In this step, process pressure ofabout 10 Torr to about 20 Torr is maintained.

2. Second Sub-Step (Step 2): Cyclic Plasma Treatment

This step is a step of performing nitrogen plasma treatment on the SiNfilm deposited on the pattern as the second sub step. In particular,this step is to increase the etch selectivity between a film depositedon an upper surface and a side surface. As described above, a plasmapower above a critical plasma power is applied to break a bondingstructure of the film on the upper surface of a pattern structure in adirection perpendicular to the direction of radical progression, wherebythe etch rate of a thin film on the upper portion is higher than that ofa thin film on the side portion.

In the disclosure, although nitrogen gas which is the same as thecomponent of the film is used, the heavier element Ar gas may be used tomore easily break the bonding structure of the film. In this step,plasma treatment is performed at a plasma power of about 700 watts toabout 1000 watts, preferably about 700 watts higher than in the firstsub-step (Step 1) to enhance radical straightness and an ion bombardmenteffect.

In addition, in order to strengthen the ion bombardment on the upper andlower surfaces rather than the pattern side, the process pressure is setlower than the pressure of the first sub-step (Step 1). In thedisclosure, the plasma treatment is performed at process pressure ofabout 1 Torr to about 5 Torr, preferably about 3 Torr. This step is alsorepeated several times (b cycles). In addition, the group step thatcombines the first sub-step and the second sub-step is repeated severaltimes (x cycles).

3. Third Sub-Step (Step 3): Post Plasma Treatment

This step is to solve the problem of non-uniform wet etchingcharacteristics in the SiN thin film. In this step, a hydrogen gas isadded to activate a mixed gas of nitrogen and hydrogen with an RF power.In order to facilitate the penetration of radicals into the film on theupper and lower surfaces of the pattern, the process pressure is lowerthan the deposition step (Step 1) and the plasma power is higher thanthe deposition step (Step 1). This step is performed at a plasma powerof 700 watts to 1000 watts, preferably 700 watts higher than a plasmapower of the deposition step (Step1) to enhance the radical straightnessand the ion bombardment effect.

In addition, the process pressure is set lower than the deposition step(Step1) in order to strengthen the ion bombardment on the upper andlower surfaces rather than the pattern side. In the disclosure, theplasma treatment is performed at process pressure of about 1 Torr toabout 5 Torr, preferably about 3 Torr. Hydrogen radicals form weakbonding with the SiN thin film or weaken the bonding structure of theSiN thin film, and an effect of weakening the bonding structure by thehydrogen radicals is maximized on a surface directly subjected to theplasma treatment. Therefore, etching resistance of a film surface may beweakened.

In addition, by supplying nitrogen radicals together, the ionbombardment of the SiN thin films on the upper and lower surfaces andthe resulting weakening of the bonding structure are enhanced. In thedisclosure, although smaller and lighter hydrogen than other elements isused, helium may also be used. In another embodiment, only hydrogen gasmay be supplied without supplying nitrogen gas.

Table 1 below shows exemplary experimental conditions applied to eachstep.

TABLE 1 First sub-step Second sub-step Third sub-step (Step 1) (Step 2)(Step 3) Gas flow Si source 1000~5000 0. 0. (sccm) (Carrier N2) ReactantN2  5000~20000 1000~20000   0~20000 H2 0. 0.  20~1000 Process Sourcefeed 0.1~0.7 0. 0. time Purge 0.5~1.0 0. 0. (sec)/cycle Plasma 3.0~5.03~60 3~60 Purge 0.1~0.3  0~1.0  0~1.0 Plasma RF Power 200~900 700~1000700~1000 (W) Freq. 13.56 MHz   100 kHz~13.56 MHz   100 kHz~13.56 MHzPressure (Torr) 10~20 1~5  1~5  Heater Temp (° C.) 300~550 300~550 300~550 

By applying the process conditions shown in Table 1 above, it ispossible to improve the etch selectivity between films deposited on theupper surface and the side surface of a pattern when depositing a thinfilm on a pattern structure. In addition, through a process ofdepositing a uniform film on the pattern by a PEALD method (firstsub-step (Step 1)), a process of breaking a bonding structure of thefilm on the upper surface of the pattern (second sub-step (Step 2)), anda process of implementing uniform etching characteristics and a highetch rate (third sub-step (Step 3)), it is possible to achieve higheretch selectivity more efficient for an RTS process than in theconventional technology.

FIG. 10 is a graph showing etching characteristics of a thin film aftera process according to the disclosure. As shown in FIG. 10, when theconditions according to the disclosure are applied, that is, when thefirst to third sub-steps (Step1+Step2+Step3) are performed, the WER isconstant regardless of time. That is, it is possible to secure aconstant WER regardless of the position in the SiN thin film.

Meanwhile, in the case of an embodiment of the first and third sub-steps(Step1+Step3), it can be seen that, although hydrogen radicals (H2 postPT) supplied during the third sub-step are effective in breaking thebonding structure of a thin film surface, a bonding structure of a deepportion of the thin film is not changed so that the WER decreases overtime.

In the case of an embodiment of the first and second sub-step(Step1+step2), it can be seen that, although nitrogen radicals (N2cyclic PT) supplied during the second sub-step are effective in breakingthe bonding structure of the deep portion of the thin film, the bondingstructure of the thin film surface is not changed so that the WER is lowat the beginning of etching, which reduces the etch selectivity.

Therefore, according to embodiments of the inventive concept, bycombining the ion bombardment effect (N2 cyclic PT) by the nitrogenradicals along with the weakening of etching resistance of the thin filmsurface (post PT) by the hydrogen radicals, the etch rate may be furtherimproved by further weakening the etching resistance over the entirethickness of an upper thin film.

TABLE 2 N2 cyclic PT N2 cyclic PT + Post PT Bottom/Side 6.3. 21.5. Etchselectivity

Table 2 shows results of the etch selectivity of the SiN thin film in awet etching time of 80 seconds in the embodiment of FIG. 10. Etching isperformed in a 100:1 DHF solution. According to FIG. 10 and Table 2above, the result according to the disclosure is increased to 21.5compared to 6.3 which is the result of cyclic plasma treatment (N2Cyclic PT) using the nitrogen radicals, thereby improving theselectivity up to 3.4 times or more. That is, by additionally performingthe plasma treatment (Post PT) using hydrogen-mixed gas (Post PT) inaddition to cyclic plasma treatment (N2 Cyclic PT) using the nitrogenradicals, the etching resistance of the film surface on the patternstructure is weakened, and then an upper surface film may be etched at auniform and high etch rate. That is, a thicker film may be left on theside of the pattern structure, so that efficient process performance maybe achieved.

FIG. 11 schematically shows the results of Table 2 above. It can be seenthat the etch selectivity is much improved (see FIG. 11B) by performingthe first to third sub-steps (step1+step2+step3) according to thedisclosure. In a case where only the first and second sub-steps areperformed, a side surface film remains below a desired thickness whilethe upper surface film is etched entirely (see FIG. 11A). However, whenthe first to third sub-steps (Step1+Step2+Step3) are performed, a filmof the desired thickness remains.

FIG. 12 is a view of a substrate processing method according toembodiments. The substrate processing method according to theembodiments may be a variation of the substrate processing methodaccording to the above-described embodiments. Hereinafter, repeateddescriptions of the embodiments will not be given herein.

Referring to FIG. 12, a source gas may be supplied during the thirdsub-step (Step3). In this step, the SiN thin film is further depositedby supplying the source gas. However, since a high plasma power issupplied during the third sub step, the ion bombardment effect becomesdominant, and the density of the newly deposited SiN thin film on anupper surface is weakened. Meanwhile, the newly deposited SiN thin filmon the side surface has a relatively weak ion bombardment effect and arelatively high density.

In addition, since a low pressure atmosphere is formed during the thirdsub-step, the ion bombardment effect is applied to a bottom surface ofthe pattern structure in addition to the upper surface. That is, sincethe density of the newly deposited SiN thin films on the top and bottomsurfaces is weakened, and the density of the SiN thin film on the sidesurface is relatively increased, the etch selectivity may be improved ina subsequent isotropic etching operation (e.g., wet etching operation).

FIG. 13 is a view of a substrate processing method according toembodiments. The substrate processing method according to theembodiments may be a variation of the substrate processing methodaccording to the above-described embodiments. Hereinafter, repeateddescriptions of the embodiments will not be given herein.

Referring to FIG. 13, operation S310 of forming a first layer isperformed. The first layer may be formed to have a uniform thickness ona pattern structure. The first layer may include a plurality of layers,and the plurality of layers may be formed by repeatedly performing acycle of an atomic layer deposition process. For example, the firstlayer may be an insulating layer.

Thereafter, operation S320 of changing a characteristic of a portion ofthe first layer is performed. For example, a bonding structure of aportion of the first layer may be changed by applying directional energyunder a first process condition. In more detail, first plasma of thefirst processing condition may be applied in a direction substantiallyperpendicular to the first layers formed on the upper and lower surfacesof the pattern structure, and due to the first plasma, a bondingstructure of portions formed on the upper and lower surfaces of thepattern structure of the first layer may be changed.

Thereafter, operation S330 of forming a second layer on the first layeris performed. In an example, at least one layer may be inserted betweenthe first layer and the second layer. The second layer may be formed tohave a uniform thickness on the first layer. The second layer mayinclude a plurality of layers, and the plurality of layers may be formedby repeatedly performing a cycle of an atomic layer deposition process.For example, the second layer may be formed of the same material as thefirst layer.

Thereafter, operation S340 of changing characteristics of portions ofthe first layer and the second layer is performed. For example, abonding structure of the portions of the first layer and the secondlayer may be changed by applying the directional energy under the firstprocess condition. In more detail, second plasma of the first processingcondition may be applied in a direction substantially perpendicular tothe second layers formed on the upper and lower surfaces of the patternstructure, and due to the second plasma, a bonding structure of portionsformed on the upper and lower surfaces of the pattern structure of thefirst layer and portions formed on the upper and lower surfaces of thepattern structure of the second layer may be changed.

Thereafter, operation S350 of reducing a difference between thecharacteristics of a portion of the first layer and the characteristicsof a portion of the second layer is performed. When the above-describedcharacteristic change operations are repeated, the lower layer receivesenergy in duplicate, resulting in a difference in characteristicsbetween the upper layer and the lower layer. For example, the degree ofchange in a bonding structure of a portion of the lower first layer maybe greater than the degree of change in a bonding structure of a portionof the upper second layer. Thus, additional operation S350 may beperformed to reduce the difference between characteristics of a portionof the first layer and characteristics of a portion of the second layer.

As an example of the additional operation S350, energy (e.g., thirdplasma) may be applied in a direction substantially perpendicular to thesecond layers formed on the upper and lower surfaces of the patternstructure, and the energy may further change the bonding structure ofportions formed on the upper and lower surfaces of the pattern structureof the second layer. In more detail, the bonding structure of a portionof the second layer may be changed by applying directional energy undera second process condition.

The second process condition is different from the first processcondition used in the above-described characteristic change operations,and in particular, the second process condition may be set so as toaffect only the bonding structure of the second layer without affectingthe bonding structure of the first layer. That is, the first processcondition may be used during the application of the first plasma and theapplication of the second plasma, and the second process condition thatis different from the first process condition may be used during theapplication of the third plasma.

By applying the third plasma using the second process condition, onlythe bonding structure of the upper second layer may be changed withoutchanging the bonding structure of the lower first layer. Therefore, adifference between the degree of change in the bonding structure of aportion of the lower first layer and the degree of change in the bondingstructure of a portion of the upper second layer may be reduced.

FIG. 14 is a view of a substrate processing method according toembodiments. The substrate processing method according to theembodiments may be a variation of the substrate processing methodaccording to the above-described embodiments. Hereinafter, repeateddescriptions of the embodiments will not be given herein.

Referring to FIG. 14, operation S510 of repeating a cycle to form a thinfilm is performed. The thin film may include, for example, a nitridefilm, specifically, a silicon nitride film. The cycle may includesupplying a first gas (e.g., a source gas) onto a substrate andsupplying a second gas (e.g., a reaction gas) that is reactive with thefirst gas.

During the repetition of the cycle, energy may be applied. Due to therepeated application of the energy, a first portion of the thin filmadjacent to the substrate may have a higher WER than that of a secondportion of the thin film away from the substrate. That is, in the thinfilm adjacent to the substrate, the energy is repeatedly applied duringthe thin film formation, thereby increasing the WER. However, the thinfilm away from the substrate may be energized only a limited number oftimes in a latter part of the thin film formation, and thus the WER maynot increase.

Therefore, additional operation S520 of offsetting such differences inWER may be performed. That is, operation S520 of reducing the differencebetween the WER of the first portion and the WER of the second portionmay be further performed. For example, by setting process conditionssuch that energy may be applied to portions adjacent to an exposedsurface of the thin film, the WER of portions adjacent to the exposedsurface of the thin film (i.e., the second portion) may be increased. Asa result, variation of WER by location of the thin film caused by thecycle repetition may be reduced, and during the subsequent wet etchingoperation S530, a uniform WER may be achieved over the entire thicknessrange of the thin film.

FIG. 15 shows an SiN thin film shape on a stepped structure according toa thin film etch rate of the above-described substrate processingmethods. FIG. 15 (a) shows the shape of a thin film before a wet etchingstate. A thin film of a certain thickness is uniformly deposited on thestepped structure.

FIG. 15 (b) shows an example of depositing and wet etching a thin filmusing the first sub-step and the second sub-step. Since etch rates ofupper and lower portions of the stepped structure at the beginning ofthe wet etching are low, an over-etch rate needs to be increased toremove both upper and lower films of the stepped structure, and thus thefilm on the side of the stepped structure becomes thinner. Therefore,when a side film of a certain thickness is required, a depositionthickness of the film needs to be increased and productivity is reduced.

FIG. 15 (b) shows an example of depositing and wet etching a thin filmusing the first sub-step and the third sub-step. The etch rate is highonly at the beginning of the wet etching, and as the etching proceeds,the etch rate rapidly decreases and converges to a certain value.Therefore, a patterning process is possible only when the thickness of aside film is thin, and when the thickness of the side film is thick, thethin film remains on the upper and lower portions of a steppedstructure.

FIG. 15 (d) shows an example of depositing and wet etching a thin filmusing the first sub-step, the second sub-step, and the third sub-stepaccording to embodiments of the inventive concept. Since the etch rateis constant and high over time, the upper and lower films of a steppedstructure may be etched in a short time to reduce side film loss. Inaddition, since the thickness of a side film remaining after the wetetching becomes greater, the applications in which the process can beapplied may be expanded.

FIG. 16 is a view illustrating a substrate processing method accordingto embodiments. The substrate processing method according to theembodiments may be a variation of the substrate processing methodaccording to the above-described embodiments. Hereinafter, repeateddescriptions of the embodiments will not be given herein.

Referring to FIG. 16, the substrate processing method may includeforming at least one layer (S110), applying plasma under the firstprocess condition (S120), applying plasma under a second processcondition different from the first process condition (S150), and purgingplasma under the second process condition (S155), followed by anisotropic etching operation (S160). Here, the plasma purging refers topurging plasma products, such as ions or radicals generated by plasma.The plasma purging operation (S155) may correspond to step t8 of FIG. 9.

By performing the operation (S155) of plasma purging under the secondprocess condition, etch selectivity of a thin film formed on a patternstructure may be improved. In more detail, the operation (S150) ofapplying plasma is performed to change a bonding structure of a portionof a thin film on the pattern structure, and activated ions or radicalsremain between pattern structures. By performing the operation (S155) ofplasma purging, plasma products remaining between the pattern structuresmay be removed.

In some embodiments, a hydrogen-containing gas may be supplied duringthe applying of plasma under the second process condition. In this case,the hydrogen-containing gas may be removed from a reaction space duringthe operation (S155) of plasma purging under the second processcondition. A hydrogen gas weakens the bonding structure of the thin filmon the pattern structure, but is also supplied between the patternstructures and affects a film deposited on the side of the patternstructure to some extent. The hydrogen gas remaining between thesepattern structures may be an inhibitory factor in improving the etchselectivity. Therefore, by carrying out the plasma purging under thesecond process condition (S155), and by removing hydrogen remainingbetween the pattern structures, it is possible to improve the etchselectivity by minimizing the effect of the hydrogen gas on the thinfilm on the side of the pattern structure.

In some embodiments, the applying of plasma under the second processcondition (S150) and the plasma purging under the second processcondition (S155) may be performed in one cycle. That is, one cycleincluding operations (S150 and S155) may be repeated a plurality oftimes such that a thin film satisfying a certain condition is formed.

FIG. 17 shows the degree of wet etching of the thin film on the sidewallof the pattern structure according to the presence or absence of theabove-described plasma purging under the second process condition(S155). FIG. 17a shows a case where there is no plasma purgingoperation, and FIG. 17b shows a case where a plasma purging operation isadded.

Referring to FIG. 17a , a thin film is formed on the pattern structurewithout performing a plasma purging. As a result of performing wetetching for 5 minutes without performing a plasma purging afterprocessing plasma under the second process condition, thin films onupper and lower portions of the pattern structure are removed, and thethickness of the thin film on the sidewall of the pattern structuredecreases from 135 angstroms to 113 angstroms. That is, it can be seenthat a wet etch rate of 4.4 Angstroms per minute is achieved.

On the other hand, in the case of FIG. 17b in which a plasma purgingoperation is added, it can be seen that the wet etch rate is lower.After forming a thin film on the pattern structure, plasma processingunder the second process condition is performed, and then the plasmapurge is carried out. After 5 minutes of wet etching, thin films onupper and lower portions of the pattern structure are removed, and thethickness of the thin film on the sidewall of the pattern structuredecreases from 142 angstroms to 130 angstroms. That is, it can be seenthat a wet etch rate of 2.4 Angstroms per minute is achieved.

As such, a hydrogen gas around the sidewall between the patternstructures is removed through the purging operation, so that theinfluence of the hydrogen gas on the sidewall may be minimized. As aresult, the weakening of a bonding structure of the thin film on thesidewall is prevented, and a technical effect of realizing high etchselectivity may be achieved.

During the plasma purging under the second process condition (S155), anitrogen gas may be used as a purge gas. That is, plasma products suchas ions and radicals may be purged by supplying and exhausting thenitrogen gas into a reaction space. In some embodiments, during theplasma purging under the second process condition (S155), vacuum purgemay be applied without a separate purge gas. In another embodiment,during the plasma purging under the second process condition (S155), thenitrogen purge gas and the hydrogen gas may be supplied together. Bysupplying the nitrogen purge gas and the hydrogen gas together, pressurefluctuation may be reduced to more stably carry out the process.

Table 3 below shows a wet etch rate in each portion of the patternstructure according to the presence or absence of the above-describedplasma purging under the second process condition (S155).

TABLE 3 no purge operation purge operation (S155) (S155) wet etch rateupper portion 73.6 58.9 (WER) side portion 13.4 3.1 (Å/min) lowerportion 68.7 63.8 etch selectivity on upper 5.5 19.0 portion/sideportion

When the purge operation is added in Table 3 above, as the hydrogen gasis removed from the reaction space, the etch rate is lowered overall,but it can be seen that etch selectivity between a film on the sidewalland a film on the upper surface of the pattern structure issignificantly improved compared to the case having no purge operation.

As described above, according to the disclosure, by adding a purgeoperation to a hydrogen plasma processing operation and removing ahydrogen gas remaining near a sidewall between pattern structures, thereis a technical effect that may improve etch selectivity between upperand side surfaces of the pattern structures.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments. While one or more embodiments have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope of thedisclosure as defined by the following claims.

What is claimed is:
 1. A substrate processing method comprising: forminga thin film on a substrate by performing a plurality of cycles, eachcycle comprising forming at least one layer and applying plasma to theat least one layer under a first process condition; and applying plasmato the thin film under a second process condition different from thefirst process condition.
 2. The substrate processing method of claim 1,setting an atmosphere such that plasma ions have directionality duringthe applying of plasma under the first process condition and theapplying of plasma under the second process condition.
 3. The substrateprocessing method of claim 1, wherein a bonding structure of a portionof the thin film is changed during the applying of the plasma under thefirst process condition, and the bonding structure of a portion of thethin film is further changed during the applying of the plasma under thesecond process condition.
 4. The substrate processing method of claim 3,further comprising an isotropic etching operation, wherein etchselectivity between the portion where the bonding structure of the thinfilm is changed and the remaining portion of the thin film is achievedduring the isotropic etching operation.
 5. The substrate processingmethod of claim 3, wherein the at least one layer is formed on a steppedstructure having an upper surface, a lower surface, and a side surfacebetween the upper surface and the lower surface, and the portion of thethin film corresponds to a portion of the thin film formed on the uppersurface and the lower surface.
 6. The substrate processing method ofclaim 5, wherein repetition of the cycles causes a difference between afirst bonding structure of a first portion of the thin film adjacent tothe stepped structure and a second bonding structure of a second portionof the thin film away from the stepped structure, and during theapplying of the plasma under the second process condition, thedifference between the first bonding structure of the first portion andthe second bonding structure of the second portion is reduced.
 7. Thesubstrate processing method of claim 5, further comprising an isotropicetching operation, wherein after the isotropic etching operation, thinfilms on the upper surface and the lower surface of the steppedstructure are removed, and a thin film on the side surface of thestepped structure remains.
 8. The substrate processing method of claim1, a hydrogen-containing gas is supplied during the applying of theplasma under the second process condition.
 9. The substrate processingmethod of claim 1, wherein the forming of the at least one layercomprises: supplying a first gas; purging the first gas; and supplying asecond gas and applying plasma to form a first layer.
 10. The substrateprocessing method of claim 9, wherein pressure in a reaction space ismaintained at a first pressure during the supplying of the second gasand the applying of the plasma to form the first layer, and the pressurein the reaction space is maintained at a second pressure lower than thefirst pressure during the applying of the plasma under the first processcondition.
 11. The substrate processing method of claim 9, wherein powersupplied during the applying of the plasma under the first processingcondition is greater than power supplied during the supplying of thesecond gas and the applying of the plasma to form the first layer. 12.The substrate processing method of claim 9, wherein the first gas issupplied during the applying of the plasma under the second processcondition that is different from the first process condition.
 13. Thesubstrate processing method of claim 9, wherein, during a first cycle,the supplying of the first gas, the purging of the first gas, and thesupplying of the second gas and applying of plasma to form the firstlayer are performed a plurality of times.
 14. The substrate processingmethod of claim 13, wherein, during the first cycle, the plasma underthe first process condition is applied to the first layer so that a WERof a portion of the first layer increases due to an ion bombardmenteffect of plasma ions.
 15. The substrate processing method of claim 14,wherein forming of a second layer on the first layer during a secondcycle after the first cycle is performed, wherein the forming of thesecond layer comprises: supplying a first gas; purging the first gas;and supplying a second gas and applying plasma to form the second layer.16. The substrate processing method of claim 15, wherein, during thesecond cycle, the plasma under the first process condition is applied tothe second layer and the first layer which is below the second layer sothat WERs of a portion of the first layer and a portion of the secondlayer increase due to an ion bombardment effect of the plasma ions,wherein the WER of the first layer is greater than the WER of the secondlayer.
 17. The substrate processing method of claim 16, wherein theplasma under the second process condition is applied toward the firstlayer and the second layer, and thus a difference between the WER of thefirst layer and the WER of the second layer is reduced.
 18. A substrateprocessing method comprising: forming a first layer; applying firstplasma to the first layer to change characteristics of a portion of thefirst layer; forming a second layer on the first layer; applying secondplasma to the first layer and the second layer to change characteristicsof respective portions of the first layer and the second layer; andapplying third plasma to the second layer to reduce a difference betweenthe characteristics of a portion of the first layer and thecharacteristics of a portion of the second layer.
 19. The substrateprocessing method of claim 18, wherein a first process condition is usedduring the application of the first plasma and the application of thesecond plasma, and a second process condition that is different from thefirst process condition is used during the application of the thirdplasma.
 20. A substrate processing method comprising: forming a thinfilm on a substrate by performing a cycle comprising supplying a firstgas onto a substrate and supplying a second gas having reactivity withthe first gas a plurality of times, wherein, due to repetition of thecycle, a first portion of the thin film adjacent to the substrate has ahigher WER than that of a second portion of the thin film away from thesubstrate; and reducing a difference between the WER of the firstportion and the WER of the second portion.
 21. The substrate processingmethod of claim 1, further comprising: purging the plasma products underthe second process condition.